Automatic couplers for rail vehicles typically comprise a drawbar that in one end is articulately attached in the chassis of a rail vehicle, and in its other end carries a coupler head having a coupling adapted to couple automatically to a correspondingly formed coupler. Usually, the coupler head has a cast coupler house in which the main shaft of the coupling is journalled. A coupling link extends forward from a central plate rotatably mounted on the main shaft and automatically engages the central plate of the meeting coupler when the couplers are brought together. For the guidance of the couplers, a guide cone serves that protrudes from the front plate of the coupler head and is received in a correspondingly shaped opening in the front plate of the meeting coupler, when the couplers approach each other.
In normal operation, the coupler head and the coupler house are subjected to repeated tensile and compressive loads that in course of time could cause fatigue of materials and joints unless these were dimensioned with safety margin. Therefore, the cast coupler house is typically a comparatively heavy component in an automatic coupler, dimensioned to resist thrust forces upon coupling at relative speeds of up to 15 km/h, as well as thrust and tractive forces that arise by repeated jerking in the coupler during travelling.